The present invention relates to an endoscope apparatus and,more particularly, to a guide mechanism for guiding an operating instrument into an endoscope to perform an operation such as, for example, a collection of a tissue from a body cavity of a subject.
In a conventionally general endoscope apparatus as disclosed in Japanese Utility Model Publication No. 58-20245, which can perform an operation such as a collection of a tissue from a body cavity, a flexible inserting portion extends from one end of an operating body, and an ocular portion is provided at the other end of the operating body. A straight guide tube is fixedly mounted on an upper portion of the operating body so as to project therefrom upwardly. A guide channel communicating with the guide tube is formed through the operating body and the inserting portion.
With the endoscope apparatus constructed as described above, the inserting portion is inserted into the body cavity, and an interior of the body cavity is viewed at the ocular portion through an objective optical system provided at a distal end of the inserting portion. When a morbid part is found, a tissue is collected, for example. Specifically, an elongated operating instrument having at a distal end thereof a pair of forceps is inserted from the guide tube into the guide channel so as to have the forceps projecting from the guide channel. The forceps are remotely controlled by an operation of an operating mechanism provided at a proximal end of the operating instrument, to allow the forceps to bite off a tissue from the morbid part.
In the above-described endoscope apparatus, it is often necessary or desirable to turn the operating body to turn the inserting portion around its longitudinal axis, to thereby alter the orientation of the inserting portion within the body cavity. The turning movement of the operating body remarkably affects the insertion and operation of the operating instrument. More particularly, when an operating surgeon holds the operating body in his natural attitude, the guide tube is oriented upwardly and, accordingly, it is easy for the operating surgeon to perform the insertion of the operating instrument into the guide tube and the operation of the operating instrument. However, when the operating body is turned to turn the inserting portion around its longitudinal axis, the position and orientation of the guide tube vary. Therefore, an unnatural attitude would sometimes be forced on the operating surgeon when he inserts the operating instrument into the guide tube or when he operates the operating instrument. This would render the operation by the operating surgeon troublesome.